Method of producing elastic fabrics



United States Patent 3,492,707 METHOD OF PRODUCING ELASTIC FABRICS Hiroyuki Segawa, Kurashiki, Japan, assignor to Kurashiki Rayon Co., Ltd., Kurashiki, Japan, a Corporation of Japan No Drawing. Filed Feb. 12, 1968, Ser. No. 704,550 Claims priority, application Japan, Feb. 16, 1967, 42/ 10,003 Int. Cl. D01d 11/06; D02g 3/32 US. Cl. 28-75 7 Claims ABSTRACT OF THE DISCLOSURE A method of producing elastic products having beautiful appearance, which comprises applying an aqueous solution of polyvinyl alcohol to the surface of polyurethane elastic filaments, subjecting the filaments to drying under the stretched state to obtain easily controllable polyurethane elastic filaments having low elongation and high Youngs modulus, making a Woven or knitted product from said filaments together with ordinary hard fiber yarns, and treating the resulting product with hot water of 60-100" C.

This invention relates to a method of producing elastic woven fabrics and knitted goods in which are used the polyurethane continuous elastic filaments.

In general, the polyurethane continuous elastic fiber has a high elongation of as much as several hundred percent and an extremely low Youngs modulus (as expressed in terms of its tenacity at 50% elongation) on the order of 001-02 gram per denier. As a consequence, in the various after treatments such as in twisting it with the other hard fiber yarns, its tension control is difficult. Hence, there tends to occur irregularities in the end product due to the fluctuation in tension such that at times it becomes practically impossible to produce the intended product.

As a result of having researched into the possibility of a method of temporarily setting the elongation of the polyurethane elastic filaments, we found according to this invention that the polyvinyl alcohol aqueous solution was most suitable as a treatment medium of the polyurethane elastic filaments and that by using this aqueous solution a pasting set effect of the elastic filaments in their stretched state could be obained, with the consequence that a temporarily low elongation and a temporarily high Youngs modulus for the elastic filaments could be obtained. Further, it was found that when the so treated polyurethane continuous elastic filaments and hard fiber yarns (e.g., nylon, polyester, etc.) are used and woven fabrics or knitted .goods are made and thereafter the so obtained woven or knitted products whose elasticity is under restraint are relaxed using hot water, the polyvinyl alcohol which had been used for paste setting of the filaments is removed and at the same time the elastic filaments themselves whose elongation had been in a temporarily set state up to this time become relaxed and shrink, whereby elasticity develops in the woven or knitted products.

An object of this invention is to temporarily effect the lowering of the elongation of a polyurethane elastic filaments While, on the other hand, raising their Youngs modulus to thereby provide a ployurethane continuous elastic filaments the management of which is simplified during their after-treatments. Another object is to provide a new method of producing high quality, fine looking woven or knitted products composed of the polyurethane continuous elastic yarns and hard fiber yarns.

Accordingly, this invention is directed to a method of producing elastic woven and knitted products which comprises applying to the surface of polyurethane continuous 3,492,707 Patented Feb. 3, 1970 elastic filaments an aqueous solution of polyvinyl alcohol having a degree of saponification of 50-100% followed by subjecting the filaments at least to drying under a stretched state ranging from at least 150% of their original length to below their breaking elongation to thereby obtain polyvinyl alcohol-coat low elongation polyurethane continuous elastic filaments having a elongation of not greater than and a Youngs modulus [expressed in terms of tenacity (g./d.) at 50% elongation] of at least 0.4 gram per denier, and thereafter making a woven or knitted product using the so obtained yarns and hard fiber yarns followed by treating said woven or knitted product with hot water of 60-100 C.

As the method of applying the aqueous solution of polyvinyl alcohol of a degree of saponification of 50- 100% to the surface of the polyurethane continuous elastic filaments, any of the customarily practiced procedures may be employed in the invention method, such as the method of dipping the elastic filaments in the polyvinyl alcohol aqueous solution, the method of spraying the filaments with the polyvinyl alcohol aqueous solution, or the method of passing the filaments between rollers whereby the polyvinyl alcohol solution is imparted to the filaments when the latter passes between the rollers. Of these, the most convenient and desirable is however the dipping method.

According to the invention, it is an indispensable condition that the polyurethane continuous elastic filaments which have been applied the polyvinyl alcohol aqueous solution, as hereinabove indicated, are dried under a stretched state ranging from at least of their original length to below their breaking elongation. A coating of polyvinyl alcohol is formed on the surface of the polyurethane continuous elastic filaments by this drying in the stretched state, and this demonstrates the etfect of paste setting the filaments in their stretched state. Thus, the polyurethane continuous elastic filaments of high elongation and extremely low Youngs modulus are converted into polyvinyl alcohol-coated low elongation polyurethane continuous elastic filaments having an elongation of not greater than 100% and a Youngs modulus [expressed in terms of tenacity (g./d.) at 50% elongation] of at least 0.4 gram per denier. These filaments have the advantage that they are very easily managed in the subsequent after treatment steps. Further, as hereinafter described, in the various modes of practicing the invention, it is possible to add the stretching and heat treatment steps modified in various ways as well as to make various modifications in the temperature conditions during the polyvinyl alcohol application and drying operations.

In carrying out the stretching of the polyurethane continuous elastic filaments in the range from at least 150% of their original length to below their breaking elongation, the spun filaments immediately after their spinning may be drawn prior to the application of the polyvinyl alcohol aqueous solution, or the stretching of the filaments may be performed after having applied the polyvinyl alcohol aqueous solution to the spun filaments or, alternatively, the application of the polyvinyl alcohol aqueous solution and the stretching may be carried out simultaneously. While the stretching can be carried out at any temperature from room temperature to a temperature just below the decomposition point of the polyurethane continuous elastic filaments, usually a range between room temperture and 100 C. is to be preferred. The temperature of the polyvinyl alcohol aqueous solution is conveniently 060 C. from the operations standpoint, but after the application the dry heat treatment is preferably carried out at 60-100 C. By means of this dry heat treatment, not only the removal of the water on the surface of the polyurethane continuous elastic filaments is carried out but also their heat treatment is concurrently accomplished.

used for the polyvinyl alcohol aqueous solution, the drying may be carried out at from room temperature to 100 C. for removing the water on the surface of filaments. This drying step or the drying and heat treatment should be carried out in all cases under tension. In practicing the invention method, it is preferred that the polyurethane continuous elastic filaments are provided a thermal history ranging from 60 C. to a temperature just below the decomposition point of the filaments,and preferably from 60100 C., during at least a certain period before the completion of the step of drying in a stretched state the polyvinyl alcohol applied to said polyurethane filaments, since such a thermal history has desirable heat treatment effects on the elastic filaments.

Further, after the drying of the polyurethanecontinuous elastic filaments, it is preferred that their cooling be carried out by holding the filaments at a temperature, e.g. room temperature, under free tension, By operating in this manner, the distortion of the residualelongation decreases and thus a shrinkage on the order of several percent to 10% occurs in the filaments.

In applying the polyvinyl alcohol aqueous solution .to the polyurethane continuous elastic filaments, the first step of the invention, the amount of the polyvinyl alcohol to be adhered to the filaments, on a dried basis, is 5200% by weight, and preferably -100% by weight, based on the filaments.

When the amount adhered of the polyvinyl alcohol is less than 5% by weight, the paste setting effect, one of the objectives of the invention, is not demonstrated fully, whereas when the amount adhered exceeds 200% by weight, the treated filaments become too thick, and difficulties are experienced in carrying out after treatment operations such as spinning. Hence, the amount adhered of the polyvinyl alcohol should preferably be held within the foregoing range.

The polyvinyl alcohol to be used in the invention is one whose degree of polymerization is 3004000, and preferably 1000-3000, while its degree of saponification is 50100%, and preferably 80100%. The degree of saponification, as here used, denotes the saponification degree of polyvinyl acetate in the production of polyvinyl alcohol therefrom. Accordingly, the above-mentioned degree of saponification of 50% indicates that 50% of the acetyl groups in polyvinyl acetate have been converted to the hydroxyl groups by hydrolysis. The concentration of the aqueous solution of polyvinyl alcohol should be 130% by weight, and preferably 520% by weight.

The polyurethane continuous elastic filaments of the invention are obtained by spinning in customary manner the polyurethane polymer obtained by the reaction of a polymer glycol having a melting point of not more than 80 C., with an organic diisocyanate and the various chain extenders. While as the spinning method the various methods of such as the dry-spinning, melt-spinning and wet-spinning methods can be employed, in the herein after given examples the polyurethane continuous elastic filaments obtained by the dry and wet-spinning methods will be described.

As the polymer glycols, useable are the polyether glycols, polyester glycols and polyetherester glycols.

Suitable polyether glycols include such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyhexamethylene glycol and the copolymers of these.

As the polyester glycols, suitable are the polycondensation products of the dicarboxylic acids such as succinic, adipic and sebacic acids with the low molecular weight glycols such as ethylene glycol, propylene glycol and butylene glycol.

The polyetherester glycols include the polycondensation products of the dicarboxylic acids, such as previously described, with such as diethylene glycol, triethylene glycol and tetraethylene glycol.

On the other hand, when a temperature of 60-100 C. is

As the-organic diisocyanates, usable arethe .polymethylene diisocyanates such as ethylene diisocyanate and hexamethylene diisocyanate, cycloalkylene diisocyanates such as cyclohexane 1,4-diisocyanate, and the diisocyanates containing an aromatic nucleus, such as tolylene diisocyanate, biphenylene 4,4-diisocyanate, diphenylmethane 4,4'-diisocyanate and 1,5-naph thylene diisocyanate.

On the other hand, the chain extenders to be used in the diamine compounds such as hydrazine, ethylene diamine, tet-ramethylene diamine, hex'am'ethylene diamine, 1,5-naphthylene diamine and p-phenylene diamine, amino alcohols such as ethanolamine-and aminoethylethanolamine, glycols such as ethylene glycol, propylen'e'glycol, 1,4-butanediol and 1,5-pentanediol, and water.

According to the invention, the so obtained polyurethane continuous elastic filaments of low elongation and high Youngs modulus are-made.into woven or. knitted products by their conjoint use with the other hard' fiber yarns. The hard fiber yarns, as here used, include'all the usual filament yarns or spun, yarns composed of natural or synthetic high molecular weight substances, as ;con tra'sted with the elastomers, and they are exemplifiedby such as polyester filaments, polyamide filaments,.,poly- Iacrylonitrile yarns, polyethylene filaments, viscose rayon and cotton fiber yarns. Further, these hard fiber yarns may be also those which have been imparted the bulky treatment.

In the process of making the woven or knitted products using the polyurethane continuous elastic filaments of low elongation treated according to the invention and the other hard fiber yarns, a blended yarn, core yarn, twisting yarn, etc., of the aforesaid two fibers can be first made andthen the woven or knitted p-roducts'be made therefrom; or the end product can be obtained by using the polyurethane continuous elastic filaments of low elongation in their as-obtained form and directly weaving or knitting these filaments with the hard fiber yarns. Again,

in making the woven or knitted products, it is also possible to use for-either the warp or weft the polyurethane continuous elastic filaments, while using'for the other'the hard fiber yarns. These woven or knitted products, as used in the invention, may be any of those forms which are conventional. In this process of making the woven or knitted products, the various apparatuses, which are usualprocess of making the woven or knitted productsyl-lence,

there is no possibility of the uneveness of tension. -C onse quently, the surface condition of the resulting woverr or knitted products is uniform andthey are in possession of a fine appearance.

According to the inventionmethod, the woven'for knitted products of various forms, obtained as hereinbefore described, 'must'be treated with 'hot water 60 C., this step being necessary for the purpose of removing the adhering polyvinyl alcohol and also for the purpose of shrinking and relaxing the treated polyurethane elastic filaments. By this hot water treatment practically all jof the adhering polyvinyl alcohol is removed anda shrinkage of 20'80% is imparted to the woven or knitted product,

thus yielding a product abounding in elasticity. One advantage of the method of the present invention is thatit 'is easily attainable to make polyurethane continuous elas tic filaments have lower elongation and high Youngs modulus by subjecting the filaments to a treatment with anaqueous solution of polyvinyl alcohol whose cost is very cheap. This results in an easy control of polyurethane continuous elastic filaments during the steps of twisting and the like, while such control is very difficult in the conventional arts.

Another advantage of the method of the present invention is that it is made possible to prepare knitted and woven articles having such a uniform and beautiful appearance as is never seen in the conventional articles by subjecting those articles composed of hard fiber yarns and said polyurethane continuous elastic filaments having a low elongation and being made easily controllable to such a simple step as that of removing polyvinyl alcohol adhered to the articles with hot water.

One skilled in the art can easily attain said advantages and others by following the method of the present invention.

The following non-limitative examples are given for further illustrating the invention.

EXAMPLE 1 The three components of polyethylenepropylene adipate having a terminal hydroxyl radical and of a molecular weight of 2000 (ethylene glycol:propylene glycol mole ratio=9:l), diphenylmethane 4,4'-diisocyanate and ethylene glycol were mixed in a molar ratio of 1:5:4, to which was then added 15% by weight of dimethylformamide as solvent to 85% by weight of this mixture. The mixture was reacted for 6 hours at 90 C. and a powdery polyurethane polymer was obtained. This was followed by the incorporation as antioxidants in the so obtained polymer of 1% by weight of 4,4'-butylidenebis(3-methyl- 6-tertialbutyl phenol) and 1.5% by weight of titanium dioxide, based on the polyurethane polymer. This was then dissolved in dimethylformamide to prepare a 28% (wt) spinning solution.

This spinning solution was extruded from a spinning nozzle having holes, each 0.25 mm. in diameter, into a stream of N gas, following which the freshly spun filaments were dried and then wound up at 350 meters per minute. The so obtained filaments had a denier of 138, a tenacity of 1.08 grams per denier, an elongation of 475% and a Youngs modulus (expressed in terms of tenacity at 50% elongation) of 0.08 gram per denier. These elastic filaments were drawn 300% at 140 C. and, while still in their stretched state, were heat treated for 30 seconds in a (wt.) aqueous solution of polyvinyl alcohol having a degree of polymerization of 1000 and a degree of saponification of 88.8%, heated to 95 C., following which the filaments, while still in their stretched state, were dried and thereafter imparted a mechanical shrinkage of 8% to obtain the treated elastic filaments. These treated elastic filaments had a polyvinyl alcohol adhesion of 43% (wt.), a denier of 51, a tenacity of 3.82grams per denier, an elongation of 64%, and a Youngs modulus of 1.87 grams per denier, and they had a high degree of form stability even under free tension.

Next, using the conventional twisting machine, a twisting yarn having a Z twist of 250 turns per meter was obtained from the three yarns of the aforesaid treated elastic yarn 51/ 1, wooly nylon 70/ 1 S twist and wooly nylon 70/1 Z twist, without stretching the treated elastic filaments hardly at all. When the so obtained yarn was unreeled from the pirn and allowed to stand under free tension, it showed little, if any, shrinkage and thus had form stability to a high degree.

To so obtained twisting yarn was then used as the warp and a mixed yarn of polyester fiber and rayon {mixture ratio of 50:50 (wt.)] was used as the weft, and a 2/2 twill weave fabric was woven. The width of the resulting fabric was 97 cm. When the polyvinyl alcohol removal and shrinkage treatment of this fabric was carried out for 30 minutes in 90 C. hot water, a 47% shrinkage took place in the longitudinal direction containing the treated elastic yarn. After it was given a finishing treatment, a longitudinally elastic fabric having a fine and uniform surface condition and an extensibility of 42% in the longitudinal direction was obtained.

Comparison The treated elastic filaments which were treated exactly as in Example 1 but Without the polyvinyl alcohol treatment had a denier of 35, a tenacity of 2.2 grams per denier, an elongation of 190% and a Youngs modulus of 0.19 gram per denier. It was thus found that a temporary lowering of the elongation and a temporary raising of the Youngs modulus such as intended by the invention were not achieved.

EXAMPLE 2 Polyurethane elastic filaments were obtained by dryspinning, as in Example 1, a polyurrethane polymer obtained by mixing polyethylene adipate (molecular weight 1900), diphenylmethane 4,4'-diisocyanate and ethylene glycol in a molar ratio of 1:5:4. The so obtained elastic filaments had a denier of 140, a tenacity of 1.2 grams per denier, an elongation of 530% and a Youngs modulus of 0.13 gram per denier.

Next, these elastic filaments were drawn 300% in a 23% aqueous solution (18 C.) of polyvinyl alcohol having a degree of polymerization of 1800 and a degree of saponification of 92% followed by allowing to stand therein for 6 seconds. The filaments were then taken out, submitted to a dry heat treatment for 20 seconds at 60 C. in their stretched state and thereafter cooled at room temperature to obtain treated elastic filaments. These filaments had a polyvinyl alcohol adhesion of 70%, a denier of 61, a tenacity of 3.5 grams per denier, an elongation of and Youngs modulus of 1.2 grams per denier.

Next, a 36s core yarn was made by means of a spinning frame from the foregoing treated elastic filaments and two ends of a slub yarn composed of 65% by weight of polyester staples of 2 denier and 51 mm. fiber length and 35% by weight of rayon staples of 2 denier and 51 mm. fiber length. The core yarn was spun under the conditions of a spindle speed of 3000 rpm, 720 twists per meter, a twist multiplier of 3.0, a front roller diameter of 28.5 mm. and a front roller speed of 47.3 r.p.m. The cone-wound treated elastic filaments were unwound from the cone longitudinally thereof and were positioned in the middle of the slub yarns in a practically unstretched state, and the core yarn was made without application of a draft. The so obtained core yarn demonstrated little, if any, extensibility. These conditions which were employed in this example for spinning the core yarn are those which are usually used when making a core yarn from hard fiber yarns.

Next, a fabric was woven using a mixed yarn of polyester and rayon fibers as the warp and in alternation the core yarn and a mixed yarn of polyester and rayon fibers as the weft. In this case, the core yarn was maintained in a practically unstretched state during the Weaving process. The resulting fabric demonstrated practically no extensibility, and when the 200-cm. wide fabric was treated in C. hot water for 30 minutes, it shrunk to a width of cm. After drying, the fabric had a uniform surface condition, and it was a laterally elastic fabric demonstrating an extensibility of 25% in the lateral direction.

EXAMPLE 3 An isocyanate-terminated polyester was obtained by reacting one mol of polyethylene adipate (molecular weight 2410) with 2 moles of 2,4-tolylene diisocyanate, following which the resulting polyester was dissolved in dimethylacetamide. This was followed by reacting the isocyanate-terrninated polyester in dimethylacetamide with an equivalent of ethylene diamine to obtain a polyurethane polymer. This polymer was dissolved in dimethylacetamide to prepare a 20% solution of the polymer, which was then wet-spun into a 70 C. water bath to obtain a polyurethane elastic filaments having a denier of 155, a tenacity of 1.02 grams per denier, an elongation of 638% and a Youngs modulus of 0.09 gram per denier.

Next, this elastic filaments were drawn 850% while spraying it with a.26% aqueous .solution (23 C.) ,of polyvinyl alcohol having a degree of. polymerization of .1750 and a degreeof saponification of 98%, following which t he.filaments were submitted to a dry heat treatment for 23 seconds at 72 C. in their stretched state and thereafter air dried to obtain treated. elastic .filaments.

These filaments whose polyvinyl alcohol adhesion was 125% had a denier-of 47, -atenacity of 2.2 grams per denier, and elongation of 95% and a Youngs modulus .of-.0.42 gram per denier. e

Next, 1' employing 'the spinning frame used in Example denier and 30 mm. fiber length.

; A .fabricwas then woven using as the .warp a mixed yarn of polyacrylonitrile fiber jand rayon (mixture ratio 1 .=50 50) and as the .weft the aforesaid core yarn and -the mixed yarn of polyacrylonitrile fiber and rayon in alternation. The fabric obtained demonstrated practically no extensibility. Whenthis fabric whose width was 175 cm. was treated for 22 minutes in 90 C. hot water, it

shrunk to 1-25 cm. After drying, the fabric became a laterallyelastic fabric having an extensibility of 27% in the lateral direction.

EXAMPLE 4 One mole of a polyetherester glycol of a molecular weight of 2600 obtained from sebacic acid and diethylene glycol and 2.1 moles diphenylmethane 4,4'-diisocyanate' were heated for one hour at 93 C., then dissolved in dimethylacetamide, after which an equimolar amount of Water was added and the mixture was reacted for 5 hours at 93C. A 20% dimethylac'etamide solution of the so I obtained polyurethane elastomer was prepared and dryspun as in Example 1. The resulting filaments had a denier of 130, a tenacity of 1.02 grams per denier, an elongation of 510% and a Youngs modulus of 0.1 gram per denier. These elastic filaments were treated in a 13% aqueous solution (15 C.) of polyvinyl alcohol having a degree of polymerization of 1300 and a degree of saponification of 87%, after which the filaments were removed from the foregoing aqueous solution and drawn 300% in customary manner, dried for 25 seconds at 75 C. in their stretched state, and thereafter cooled at room temperature to obtain treated elastic filaments, which had a polyvinyl alcohol adhesion of 77%, a denier of 41, a tenacity of 2.9 grams per denier, an elongation of 93% and a Youngs modulus of 0.95 gram per denier.

These filaments were submitted to a doubling and twist-' ing operation as in Example 1 to obtain a 210 twists per ,meter Z twist twisting yarn. A 2/ 2 twill weave fabric was woven using this yarn as the warp and a mixed yarn of polyester fiber and rayon as the weft. The width of the resulting fabric 'was 150 cm. Whenthis fabric was heat treated for .minutes in hot water (91 C.), the polyvinyl alcohol was removed and at'the same time a shrinkage of 31% took place in the warp direction. The result- -.-ing fabric had an extensibilityof 21% i h longitudinal direction. I t

EXAMPLE 5 The undr'awn, still unheat-treated elastic filaments ob- 'tained in Example 1, having a denier of 138, atenacity of "1.08 grams per denier, an elongation of 475% and a Youngs modulousof 0.08 gram per denier were drawn in a 12% aquous solution (90 C.) of polyvinyl "alcohol having a degree of polymerization of 2500 and a degree of saponification of 95% followed by heat treating for 15 seconds to obtain treated elastic filaments. The

so obtained treated elastic filaments had a polyvinyl alcohol adhesion of 18%, a denier of 46, a-tenacity' of 18 grams per denier, an elongation of 66% and a Youngs modulus of 1.48 grams per denier. They possessed a high degree of form stability even under free tension and demonstrated practically no extensibility. These treated elastic filaments and a 50 denier yarn of polyamide fiber (nylon) were warped by meansof .a tricot warper v with the treated elastic filaments in a practically unstretched state and then wound up on two sets of beams. Guides were provided in two places during .the,warping step but practically no tension irregularities ascribable to the guides appeared in the treated elastic filaments. Next, a tricot knitting machine was used and a half tricot having a machine Width of280 cm. was made, the design being such that the nylon would be in the front while the treated elastic filaments would be in the back. It was possible to carry out this knitting; operation quite smoothly. The so obtained half tricot wastreated for 30 minutes in a 70 C. water bath containing Scourol: (a nonionic surfactant of polyethylene glycol ether, a product of Kao Soap Company, Japan) as thescouring agent, then treated for 15 minutes in C. boiling water containing Scourol, followed by washing in 60 C. hot water, drying for one minute at 100 C. at a constant length and thereafter setting for one minute at 170 C. at a contant length to obtain a 165-cm.-Wide product. As compared with the product in which only nylon was used, this prod- --uct had a soft feel and fine appearance as well as an extensibility of 59%. No irregularities ascribable to the tension irregularity of the elastic filaments could be observed in this product.

Iclaim: v I

1. A method of producing an elastic fabric which consists essentially of applying to the surface of polyurethane continuous elastic filaments an aqueous temporary setting solution of polyvinyl alcohol having a degree of saponification of 50-100 and subjecting the filaments to drying under a stretched state ranging from at least percent of the original length of said filaments to below the breaking elongation thereof to thereby obtain polyurethane continuous elastic filaments of low elongation coated with said polyvinyl alcohol whose elongation is .not greater than 100% and whose Youngs modulus as w expressed in terms of tenacity in grams per denierat 50% elongation is at least 0.4 gram per denier, and thereafter making a'fabric using the thus obtained filaments with hard fiber yarns, followed by treating the resulting fabric in hot water of 60-100 C. to remove the polyvinyl alcohol setting solution from the surface of said polyurethane filaments thus yielding an elastic fabric.

- 2. The method according to claim. 1 wherein said aqueous solution of polyvinyl alcohol is a concentration of 1-30 percent by weight and the amount applied of said polyvinyl alcohol -is 5200 percent by weight based {on the filaments. I 1.

3. The-method according to claim 1 wherein the polyvinyl alcohol is adhered to the surface of said polyurethane continuous elastic filaments by dipping said filaments in said polyvinyl alcohol aqueous solution.

4. The method according to claim 1 wherein the temperature of said polyvinyl alcohol aqueous solution to be applied is 100 C. I

5.'The method according to claim 1 wherein the polyurethane continuous elastic filaments are concurrently subjected to drying and heat treatment by using a drying temperature of 60l00 C. V

, 6. The method according to claim 1 which comprises exposing said polyurethane continuous elastic filaments 'in their stretched state to a temperature ranging from 60 C. to a temperature just below the decomposition 'tem 9 10 7. The method according to claim 1 wherein said hard 3,093,504 6/ 19 63 Bode 28-75 fiber yarns are yarns which have been subjected to a 27,192 4/1966 Grifliths 28--75 X t bulking reatment FOREIGN PATENTS References Cited 5 710 507 6/1965 C d am 21. UNITED STATES PATENTS 552,190 5/1943 Great Britain.

2,157,463 5/1939 Shepherd. LOUIS K. RIMRODT, Primary Examiner 2,427,334 9/1947 Alderfer, 1 1 2,852,834 9/1958 Engelhard. 0 28--76 

